Two-way flow control valves presently commercially available are either flow control valves found in cartridge type constructions, configured as continuous flow control valves, or are flow control valves in housing type constructions.
With the flow control valves embodied in cartridges, various different measuring diaphragms with variable diameters are required to control the throughput flow throughout the entire area of application which comes into consideration. Independent control or adjustment over the entire area of application is therefore not possible. The fine setting of the volume of the flow in these valves occurs within a throughput area defined by the diaphragm by means of variation of the tension, and concurrently by modification of the required adjustment pressure differential. Various different diaphragms must be provided for different flow characteristic factors, so that the readiness-maintenance and the continuous maintenance of the measuring diaphragm is costly. Also, with flow volume modification over the adjustment area, the valve must be opened. Thus some means of engagement in the inside valve structure is to be undertaken.
On the other hand, in the case of flow control valves in housing structures of the traditional type, the flow can be adjusted over the entire area of application without exchange of the measuring diaphragm. However, this is attained by a constructively costly structures with noncontinuous operation of the means for independent adjustment of the volume of the flow (measuring diaphragm) and the correcting member (operating piston). The measuring diaphragms which are used in this case are configured as independently adjustable impedance (or butterfly) valves, which vary the diameters of the measuring diaphragms. The operating piston or piston manometer is arranged externally in a suitable receiving bore. Auxiliary bores are required in somewhat detailed arrangements for connection of the operational units. With these types of flow control valves, the measuring diaphragm and the piston manometer are arranged in a housing structure. Auxiliary bores and/or compound-filled annular passages are also required in this case. Consequently, an unfavorable flow guide begins to form in the valve, so that a relatively small area of application in comparison with the dimensions of the structure is involved in the valves of this type. Also, the types of structures disclosed in this case are of costly construction and considerable volumes are required.
For flow control valves in cartridges and for flow control valves in housing structures, the possibility exists of working with two sets of guides. However the danger of jamming arises, which can cause erroneous function when these valves are used.